From a prior development a safety closure is known, published Nov. 25, 1982 in the international patent application No. PCT/EP82/00100, which has the feature of an interengagement effected between radial rib-shaped teeth on the inner surface of the skirt portion of the outer cap with radial rib-shaped teeth provided on the outer surface of the skirt portion of the inner cap and whereby exerting a downward pressure upon the outer cap and against spring operation of lips engaged with a conical surface and by a simultaneously effected rotational movement of the outer cap, a co-rotation of the inner cap is caused which enables onscrewing or unscrewing of the safety closure.
A disadvantage for onscrewing of this prior closure upon a container mouth is the requirment to press down the outer cap for interengaging the inner and outer caps before rotation of the outer cap can be transmitted to the inner cap. The user must thus be informed of the instruction "press down" (for onscrewing) and he must repeatedly keep in his mind while onscrewing the closure to press it down initially and to maintain it pressed down.
It is the object of the invention to improve the prior closure as described before in such a manner as to avoid the necessity of providing instructions for onscrewing and to enable the user to easily onscrew without any special instructions or considerations.
According to the present improvement and invention a safety closure of the aforementioned type is especially constructed and characterized in that the surface of the intermediate wall portion on the inner cap which is facing the cylindrical portion is peripherally spaced, provided with radial rib-shaped teeth whereas each of the inwardly protruding circumferentially spaced lips on the outer cap is provided on its surface facing the intermediate wall portion with a tangentially extending protrusion having a length in the axial direction which is less than the length of said lips, but great enough for these protrusions to interengage the radial, rib-shaped teeth on the inner cap in all relative positions of the two caps. That is, whether pressure is being exerted upon the outer cap of the closure or not.
By this novel invented safety closure, the provision of the described additional teeth creates an interengagement even at no downward pressure on the outer cap and this ensures a more powerful cooperation between the inner and outer caps.